The present invention pertains to loudspeaker enclosures of the low frequency exponential folded horn type intended for corner placement.
The current audiophile interest in high efficiency loudspeakers and enclosures that maximize speaker efficiency are again making older proven technologies potentially profitable if an appropriate balance of performance, versatility, cost and ease of manufacture can be attained. With the addition of the “Home Theatre” consumer market, there is another potential economic avenue for large loudspeakers whose performance approaches the overall sound quality as one might find in commercial theatres.
It is well known in the art that corner placement of loudspeakers provides the most efficient reproduction of low bass notes. The projection of bass waveforms into a π/2 solid angle allows for the reduction of the physical size of the loudspeaker horn enclosure by 8 times. This allows a bifurcated exponential horn folded to use the corner walls as part of the horn itself with a nominal low frequency cutoff (Fc) of 40 Hz to be achieved in a relatively compact enclosure.
The U.S. Pat. No. 2,373,692 to Klipsch teaches what has become a time-proven design that, while providing a true 40 Hz cutoff exponential horn in the smallest possible footprint, it provides access to the horn throat from one side only, and is specifically designed for and is limited to only one topology of use. It should be noted, however, that the Klipsch invention is still in commercial production and has remained the de facto performance and production standard for this genre of loudspeaker for over 50 years.
The U.S. Pat. No. 2,815,086 to Hartsfield teaches a corner horn design featuring top access to the horn throat, but the design is complex and complicated to build, and has been out of production for decades. It also features an alternative use intermediate horn that allows for the bass horn cabinet to be used to rear-load a full-range driver.
Both of the above cited prior art examples are known in the art as front-loaded exponential horns, in that the front of the driver feeds directly into the horn throat (whether with or without a filtering cavity), and the back chamber for the driver is sealed from the atmosphere (with the exception of the alternative Hartsfield configuration as described previously).
The formulas for calculating the values of exponential horns are well known in the art. Such examples can be found in the text “How to Build Speaker Enclosures”, by Alexis Badmaieff and Don Davis, Howard W. Sams and Company, Indianapolis, Ind., 13th printing (1978) pages 86 through 91.
Whereas both of the previously cited examples of the prior art may be purchased new today from various sources, the retail prices involved are daunting, most likely due to the complexity of the designs and the resulting need for highly skilled labor. Therefore, the need exists for a less complicated method of achieving relatively the same performance at a reduced cost.